Key cases of various configurations have been used for many years to minimize the inconveniences of storing and operating keys which hang loose from a key ring. Loose keys are noisy, may poke holes in pockets, and may cause inconvenience in locating and selecting a particular key when needed. Additionally, loose keys can scratch the finish of, e.g., the area of a car door adjacent to the lock when unlocking or locking the door.
Prior art key cases have addressed these concerns with varying degrees of success. Many cases hold all keys other than the one being used during operation to minimize or eliminate scratching of surfaces adjacent the keyhole, but these key cases often increase the difficulty of selecting the key to be used and sometimes require the user to replace the key in the case in an exact way. Cases can also be bulky and heavy which make them unsuitable for placement in, e.g., a pants pocket. Binding and tangling of keys in the case can also be a problem.
Another concern with some key cases is that they do not allow for complete ejection of the key from the case. This can be a problem with regard to certain automobile ignition key receptacles into which the entire head of the key must be inserted. It is also desirable to be able to select and replace keys in the case with only one hand, eliminating the need to set down grocery bags, babies, books, briefcases, or other objects which the user may be carrying. Convenience of installation and removal of the keys in the case is also a concern.
A particular class of key cases comprises a housing into which the key is placed, which housing has a slot running longitudinally down its side. A device holding the top of the key is attached to a protrusion of some kind through the slot, enabling the user to slide the key into and out of the casing by moving the protrusion. References disclosing this type of key case include Gebert U.S. Pat. No. 4,951,819, Friedland U.S. Pat. No. 4,307,590, Hinkle U.S. Pat. No. 3,464,244, and Stifelman U.S. Pat. No. 3,354,678. Many of these kinds of cases retain some or all of the disadvantages outlined above, and binding and mis-alignment of keys in the cases is a common problem. In addition, some of these cases allow for storage of only one key or provide various compartments each holding only one key, creating obvious disadvantages of limited use or bulk. Other types of key cases are disclosed in Gebert, U.S. Pat. No. 4,934,521, and Leopoldi et al., U.S. Pat. No. 4,281,527.